1. Field of the Invention
The present invention relates to a vibration type driving apparatus relatively driving an elastic member and a contact member contacting the elastic member.
2. Description of the Related Art
A vibration type driving apparatus (e.g., ultrasonic motor) causes an elastic member with a piezoelectric element fixed thereon to excite progressive and standing oscillatory waves by application of an alternating-current voltage to the piezoelectric element, thereby rotating a rotor kept in contact with the elastic member.
In Japanese Patent Application Laid-Open No. H05-252767 and Japanese Patent Application Laid-Open No. H09-289785 are disclosed vibration type driving apparatuses in which a frictional member is provided in an area of an elastic member contacting a rotor, and for the material of the frictional member, polymeric materials and metallic materials are used.
In a conventional rod type vibration type driving apparatus, the surface of an elastic member made of brass is coated with an electroless nickel plating containing silicon carbide particles having a wear resistance. Alumite with aluminum subjected to an anodization treatment is used as a rotor. However, in the vibration type driving apparatus formed of the materials described above, drive time was relatively short for inhibiting an increase in wear loss amount.
Thus, in Japanese Patent Application Laid-Open No. H10-42579 is disclosed a vibration type driving apparatus in which a frictional member is formed of ceramics excellent in wear resistance property, specifically aluminum oxide ceramics which is easy to obtain and inexpensive, for improving the lifetime of the frictional member and making it possible to use the frictional member in a wide range of applications. In this case, compared with the case where the electroless nickel plating containing silicon carbide particles is coated, the wear resistance is improved, thus making it possible to improve the lifetime of the vibration type driving apparatus.
In Japanese Patent Application Laid-Open No. 2003-134858, Japanese Patent Application Laid-Open No. 2003-199376 and Japanese Patent Application Laid-Open No. 2003-209983 is proposed a vibration type driving apparatus downsized so that the vibration type driving apparatus can be mounted on a small-sized device.
However, the aluminum oxide ceramics is poor in toughness compared with metallic materials, and therefore if the frictional member is formed of the aluminum oxide ceramics, cracking and chipping tend to occur in a production step such as processing. Moreover, it may be impossible to obtain a sufficient wear resistance in the drive of the vibration type driving apparatus.
Particularly, in the downsized vibration type driving apparatus, further enhancement of strength is required for an improvement in reliability of the elastic member, and development of a material resisting cracking and chipping and showing high strength and high toughness is desired for an abrasive member. The need for reduction of costs for the vibration type driving apparatus is strong, and it is thus preferable that material costs and production costs are low.